When soap is scru

Curry contains turmeric which acts as an acid-base indicator. Turmeric contains yellow dye, which turns red in basic solutions when soap is scrubbed on a stain of curry on a white cloth. This is due to the fact that soap solution is basic in nature which changes the colour of turmeric in the curry stain to red-brown. This stain turns to yellow again when the cloth is rinsed with plenty of water because then the basic soap gets removed with water.